Study On Preparation And Properties Of Calcium Iodate And Sodium Selenite Microcapsules For Feeds

Microencapsulation of feed additive is one of the effective ways to enhance the utilization rate of feed additive.Calcium iodate and sodium selenite are generally used to feed additives in animal husbandry.However,calcium iodate and sodium selenite have poor stability in the application process,resulting in a low utilization rate and resource waste.To this end,calcium iodate and sodium selenite were microencapsulated by different methods and their properties were analyzed.In order to improve the stability of calcium iodate and sodium selenite,and improve the utilization of both and reduce the waste of resources.The main work of this paper is as follows:Calcium iodate/sodium alginate microcapsules（CIAMs）were prepared by improved emulsification/internal gelation.The preparation process of CIAMs has optimized:the concentration of sodium alginate was 12 g·L^-1,and the mass of Nano-CaCO₃ was 1/2 of that of sodium alginate.The volume ratio of continuous phase to dispersed phase=3:1,and the mass of Span 80 was 2%of the continuous phase and 1.2 g Ca（IO₃）₂ were added.500r·min^-1 was stirred for 30 min,then the dispersed phase was added and emulsified for 90min.The molar mass ratio of glacial acetic acid to Nano-CaCO₃ was 6.9:1 and crosslinked for 25 min.The loading content of calcium iodate and encapsulation rate of CIAMs were41.0%and 71.8%,respectively.After Ca（IO₃）₂ and CIAMs were added to the vitamin C salt solution,t_50%of the time for vitamin C decomposition was 54.8 min and 78.3 min,respectively.CIAMs has the ability to significantly improve the stability of Ca（IO₃）₂ in the presence of reducing substances.Sodium selenite/sodium alginate microcapsules（SSAMs）were prepared by improved emulsification/internal gelation.Selenite was embedded in microcapsules in an amorphous state.Diffusion type of water molecules changes from Non-Fickian to FickianⅠwhen the temperature rises from 30°C to 50°C.Diffusion type of water molecules is FickianⅠwhen ion concentration is 0.3 mol/L and pH1or pH13,but it was changed to Non-Fickian when ion concentration is 0 or 0.6 mol/L and pH7.Schott model was used to fit the swelling behavior of SSAMs,and its correlation coefficient reached above 0.99.SSAMs are responsive to ion concentration,pH,and temperature.The preparation process of SSAMs was optimized:the concentration of sodium alginate was 18 g/L,he volume ratio of continuous phase to dispersed phase=4:1,and the mass of Span 80 was 3%of continuous phase was added as the continuous phase.After emulsion for 40 min,glacial acetic acid was added to crosslink for 15 min.Loading content of Na₂SeO₃ and encapsulation rate of SSAMs was 16.2%and 52.7%,respectively.Calcium iodate/chitosan microcapsules（CICSMs）and sodium alginate@calcium iodate/chitosan microcapsules（SA@CICSMs）were prepared by phase separation and electrostatic self-assembly.The cumulative release rate of calcium iodate in the non-enzymatic simulated gastric juice,ultra-pure water and non-enzymatic simulated intestinal juice of CICSMs was similar,but the release rate of calcium iodate in the non-enzymatic simulated gastric juice was much higher than that in the non-enzymatic simulated intestinal juice and ultra-pure water.While the release rates of calcium iodate by SA@CICSMs non-enzymatic simulated gastric juice,ultra-pure water and non-enzymatic simulated intestinal juice were similar,but the cumulative release rates were significantly different.Under the corresponding conditions,the cumulative release rates of calcium iodate were 79.78%,89.37%and 96.95%,respectively.The release process of CICSMs and SA@CICSMs is pH-responsive.The release process of CICSMs in non-enzyme simulated gastric juice conforms to the first-order release kinetics.The release process of CICSMs in ultra-pure water or non-enzyme simulated intestinal fluid is more consistent with Higuchi release kinetics.Under the experimental conditions in this paper,the process of releasing calcium iodate by SA@CICSMs was Non-Fickian diffusion.CICSMs and SA@CICSMs had the obvious gastrointestinal fluid response.Calcium iodate and sodium selenite microcapsules are expected to be new forage iodine and selenium nutrients.After Ca（IO₃）₂,CICSMs and SA@CICSMs were added to the vitamin C salt solution,t_50%of the time for vitamin C decomposition was 177.1,264.9 and 225.8 min,respectively.Both of CICSMs and SA@CICSMs have the ability to significantly improve the stability of Ca（IO₃）₂ in the presence of reducing substances.